Interlocking system for railroads



P 1935- A. R. WHITEHORN 2,014,347

INTERLOCKING SYSTEM FOR RAILROADS Filed July 29, 1932 WM @Mw, ATTQRNEY Patented Sept. 10, 1935 UNITED STATES INTERLOCKING SYSTEM FOR RAELROADS Arthur R. Whitehorn, Rochester, N. Y., assignor to General Railway Signal Company, Rochester, N. Y.

Application July 29, 1932, Serial No. 626,069

2 Claims.

This invention relates to railway interlocking systems and more particularly toa time locking means for a track switch control lever in such a system.

* In railway interlocking systems it is well known that the operation of certain traflic controlling devices is prevented during certain conflicting positions of other associated traffic controlling devices, or for example, a signal control lever while 101 in a position to clear its associated signal which governs traffic movements over a certain switch prevents operation of the control lever for this switch until the signal has been put to stop. In addition to this interlocking of levers which is usually accomplished by well known mechanical means, a detector locking of the track switch is provided which is arranged to prevent operation of the switch while a train occupies a certain section of track including the switch. l-lowever, it has been found dangerous to permit a movement of a track switch to a new position immediately after changing the associated signal from clear to stop, because an approaching train may accept the signal clear, and if the speed of the train is comparatively high, it may not be possible to stop short of the switch, which may have been moved or partially moved after placing the signal to stop, but before the train has entered the aforesaid detector track section.

' In view of the above and other considerations, it is proposed in accordance with the'prcsent invention to provide an interlocking system which enforces that a period of time elapse between changing of a signal indication from clear to stop and the movement of an associated track switch, and it is proposed to enforce this time element by preventing the movement of the signal control lever to a position which unlocks or permits movement. of the switch control lever until the signal has displayed a stop indication for a predetermined. period of time.

One specific embodiment of the invention is illustrated in the accompanying drawing in a simplified and diagrammatic manner, more with the object of making it easy to understand the nature of the invention than for the purpose of illustrating the specific construction of the devices preferably employed in a practical application of the invention.

A section of railway track has been shown in the accompanying drawing which includes atrack switch TS operated by aswitch machine SM with signals G G and G3 arranged to govern trafflC movements over the switch TS. A control re lay CG is arranged tocontrol the indication displayed by the signal G which relay CG is in turn controlled by the signal control lever SGL arranged in an interlocking tower in the conventional manner. It is also understood that the signals G and G are likewise controlled by simi- .5-

lar interlocking levers and their accompanying control circuits which have herein been omitted to simplify the disclosure.

The lever SGL is interlocked mechanically to other levers controlling conflicting traific controlling devices such as the control lever for operating the switch machine SM with which the present invention is particularly concerned. This mechanical locking is accomplished through the usual tappet rod T having a roller at its 15v upper end which rests in a slot S in the control lever SGL shaped as shown on the drawing. It is now well known in the art that the tappet'rod 'I is forced up and down by the lever slot S during operation of the lever SGL to its 20 extreme positions and that this vertical actuation of the rod T is effected by mechanical locking means to lock or release other switches orsignals which conflict with the signal G, or for example the lever SGL must be in its full 25 normal position N which forces the tappet rod T to its extreme lower position as shown before the switch control lever can be moved to change the position of the track switch TS.

An indication magnet IM is associated with the lever SGL which operates a lock rod L, the upper end of which rod L rests in a second slot LS in the lever SGL which slot is so shaped that movement from the reverse position R to the full normal position N of the lever is prevented until the indication magnet IM has been energized.

The simple locking means for enforcing that an indication magnet may be'energized to permit the full normal movement of the lever has been shown merely for example, and it is to be understood 40 that other types may be used as well, such as the trigger. type locking means disclosed in the patent to John B. Taylor, No. 752,127 dated February 16, 1904.

trol relay" CG, and back to the opposite terminal Ci of the same-source of energy. This circuit picks up the relay CG which energizes the clear signal light over a circuit from one terminal B of a source of energy, front contact 1 of the signal control relay CG, wire 8, through the clear signal light 9 to the opposite terminal C of the source of energy.

In this manner the signal G is controlled in accordance with the position of its control lever SGL, and as previously mentioned the interlocking means operated by this control lever through the tappet rod T is now efiective to prevent operation of control levers of other conflicting traffic controlling devices such as the control lever for the switch machine SM which is not shown in the accompanying drawing to simplify the disclosure. Consequently, when it is desired to ,move the track switch TS, the lever SGL must be returned to its full normal position N before the switch control lever can be moved, but in operating the signal control lever SGL to the reverse position the indication locking means L is forced down by the inclined portion 4 of the slot LS thereby stopping the normal movement of the signal lever SGL at the indicating position NI by the shoulder l which engages the locking means L.

The lever SGL being operated to its indicating position NI de-energizes the signal control relay CG by interrupting its energizing circuit at contact 5, which relay CG then drops to display a danger signal over a circuit from one terminal B of the source of energy, through back contact I of relay CG, wire ll, through the red signal light I2 to the opposite terminal 0 of the source of energy. An indicating circuit is now completed for energizing a thermal timing relay TR from the terminal B of the source of energy, through back contact M of relay CG, over the indication wire IW, through the lever contacts l closed by the movable contact 13 in its normal indicating position NI, over wire I 6, through the heating coil I! of the thermal relay TR, wires l8 and I9, through the operating magnets of the indication locking means IM to the opposite terminal C of the source of energy.

The current flowing in the above traced circuit is sufficient to heat the element 11 of the thermal relay TR, but is not sufiicient to attract the armature 20 of the indication magnet IM, and consequently after a predetermined period of time, the heat from the element I! will actuate the bimetallic element 2| to close the front contact which it constitutes. The closing of contact 2| shunts the heating coil l1 and increases the current in the previously traced circuit to an amount which is effective to attract the armature 20 of the indication magnet IM and force the locking means L upward to a position allowing the lever SGL to be moved to its full normal position N as shown in the drawing. The lever SGL then being in its full normal position unlocks the confiicting levers such as control lever for the switch machine SM and also interrupts the energizing circuit for the indication magnet IM at contact [5 which is shaped as shown in the drawing or so that its movable contact l3 does not contact with the stationary contacts [5 when the lever SGL is in the full normal position.

The control levers for the signals G and G which are not shown herein, are mechanically interlocked with the control lever for the track switch TS in the same manner as the lever SGL. Each of these signal control levers will then be arranged with a time locking means in the same manner as the lever SGL thereby enforcing that a stop indication be displayed by all signals governing traffic over the switch TS, and that such stop signal be displayed for a predetermined length of time before the control lever for the switch TS can be removed. 5

A simple and inexpensive time locking means for an interlocking system has thus been provided which enforces the lapse of time between placing the control lever to a stop indicating position and moving such a lever to a position which unlocks conflicting levers. The system also inherently provides that such an element of time must be initiated by an indication originating from the location of the associated traflic controlling device which indication must correspond to the position of the control lever, and that such an indication must be present for a predetermined length of time before it is effective to release the control lever to permit a movement to a position which unlocks conflicting traflic controlling devices. The enforcing of this time interval obviously permits a route to be changed without endangering any traffic movement already started before such a change in as much as a train which cannot stop short of the track switch after receiving a restricted signal has suflicient time to enter a detector track section to block movement of the switch thereby either enabling the movement to be executed or enabling the train to return to the rear of the signal.

The above rather specific description of one form of the present invention is given solely by the way of example, and is not intended in any manner whatsoever in a limiting sense. It is also to be understood that various modifications, adaptations and alterations may be applied to meet the requirements of practice, without in any manner departing from the spirit or scope of the present invention, except as limited by the appended claims.

Having thus shown and described my invention, what I claim is:

1. In combination, a traffic controlling device, an interlocking lever for controlling said device, lock means for preventing an extreme movement of said lever, a releasing circuit including a line wire extending from said lever to said device for releasing said lock means and including a contact indicating a particular condition of said trafiic controlling device and including a contact closed by the lever when the lever is in position corresponding to the particular condition of said traffic controlling device, a timing device adjacent said lever for controlling said releasing circuit, and an energizing circuit for said timing device including said line wire and both of said contacts in series.

2. In combination; a railway signal; a lever for controlling said signal and having an extreme position beyond the stop position to which it cannot be moved unless a lock magnet associated with said lever is energized; a signal contact associated with said signal closed when said signal assumes the stop condition; a lever contact closed when said lever assumes the stop position; a circuit for said lock magnet including a source of current, said signal contact, said lever contact and also including an impedance high enough so as not to allow actuation of said lock magnet upon closure thereof; and slow-acting means controlled by said circuit for shunting said impedance a predetermined time after closure of said circuit, to eifect actuation of said lock magnet.

ARTHUR R. WHITEHORN. 76' 

